Images are invariably viewed in one of three ways; as a front illuminated print, such as a book, magazine or photograph, a rear illuminated device such as a television set or computer monitor, or as a film or digitally projected image such as a slide presentation or motion picture. The present invention relates to printed or reflected media as in the first example.
Accuracy and control of colour reproduction is important in many fields and vital in medical diagnosis, law enforcement and security. It is also highly desirable that anyone with minimal technical skills and normal colour vision be able to evaluate the accuracy of image reproduction in colour printing equipment and to be able to correct errors in colour image reproduction.
Light sources are typically designated as falling into one of three or four Kelvin categories, depending on the colour temperature of the light—illuminant A for Tungsten, 5400K for direct sunlight, and 6500 K for skylight. While image matching using traditional full spectrum illumination sources such as tungsten and daylight from the sun have been problematic, the issue has been seriously exacerbated with the introduction of discontinuous light sources such as fluorescent and LED illuminants.
Such discontinuous illuminants can produce images wherein certain colours, failing to receive light (visible electromagnetic radiation) at the correct wavelength, will reproduce said colours inaccurately.
The discontinuous illuminant issue can be further complicated by the spectral reflectivity of the pigments, dyes and media used in the image reproduction process.
The present invention is designed to identify and enable quantification and adjustment of such issues, by adjustment of printing equipment settings.
Typical image evaluation systems designed to address accuracy of colour reproduction in colour printers do so electronically by sensing the brightness, hue and saturation of a test image.
Such systems rely on the accuracy and consistency of the sensors and associated electronic equipment, which can require frequent re-calibration from an expert technician and evaluating the data from such systems requires experience to interpret the results.
This invention is designed to overcome these limitations by providing apparatus and software using well-established principles and technology in a system that is intuitive and easy to use by anyone having normal colour vision.